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  • Pass the return type as a parameter in java?

    - by jonderry
    I have some files that contain logs of objects. Each file can store objects of a different type, but a single file is homogeneous -- it only stores objects of a single type. I would like to write a method that returns an array of these objects, and have the array be of a specified type (the type of objects in a file is known and can be passed as a parameter). Roughly, what I want is something like the following: public static <T> T[] parseLog(File log, Class<T> cls) throws Exception { ArrayList<T> objList = new ArrayList<T>(); FileInputStream fis = new FileInputStream(log); ObjectInputStream in = new ObjectInputStream(fis); try { Object obj; while (!((obj = in.readObject()) instanceof EOFObject)) { T tobj = (T) obj; objList.add(tobj); } } finally { in.close(); } return objList.toArray(new T[0]); } The above code doesn't compile (there's an error on the return statement, and a warning on the cast), but it should give you the idea of what I'm trying to do. Any suggestions for the best way to do this?

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  • How should I map an abstract class with simple xml in Java?

    - by spderosso
    Hi, I want to achieve the following xml using simple xml framework (http://simple.sourceforge.net/): <events> <course-added date="01/01/2010"> ... </course-added> <course-removed date="01/02/2010"> .... </course-removed> <student-enrolled date="01/02/2010"> ... </student-enrolled> </events> I have the following (but it doesn't achieve the desired xml): @Root(name="events") class XMLEvents { @ElementList(inline=true) ArrayList<XMLEvent> events = Lists.newArrayList(); ... } abstract class XMLEvent { @Attribute(name="date") String dateOfEventFormatted; ... } And different type of XMLNodes that have different information (but are all different types of events) @Root(name="course-added") class XMLCourseAdded extends XMLEvent{ @Element(name="course") XMLCourseLongFormat course; .... } @Root(name="course-removed") class XMLCourseRemoved extends XMLEvent { @Element(name="course-id") String courseId; ... } How should I do the mapping or what should I change in order to be able to achieve de desired xml? Thanks!

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  • Weird behaviour with Scanner#nextFloat

    - by James P.
    Running the following in Eclipse initially caused Scanner to not recognize carriage returns in the console effectively blocking further input: price = sc.nextFloat(); Adding this line before the code causes Scanner to accept 0,23 (french notation) as a float: Locale.setDefault(Locale.US); This is most probably due to regional settings in Windows XP Pro. When the code is run again 0,23 is still accepted and entering 0.23 causes it to throw a java.util.InputMismatchException. Any explanation as to why this is happening? Also is there a workaround or should I just use Float#parseFloat? Edit: import java.util.Locale; import java.util.Scanner; public class NexFloatTest { public static void main(String[] args) { //Locale.setDefault(Locale.US); //Locale.setDefault(Locale.FRANCE); // Gives fr_BE on this system System.out.println(Locale.getDefault()); float price; String uSDecimal = "0.23"; String frenchDecimal = "0,23"; Scanner sc = new Scanner(uSDecimal); try{ price = sc.nextFloat(); System.out.println(price); } catch (java.util.InputMismatchException e){ e.printStackTrace(); } try{ sc = new Scanner(frenchDecimal); price = sc.nextFloat(); System.out.println(price); } catch (java.util.InputMismatchException e){ e.printStackTrace(); } String title = null; System.out.print("Enter title:"); try{ title = sc.nextLine(); // This line is skippe } catch(java.util.NoSuchElementException e ){ e.printStackTrace(); } System.out.print(title); } }

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  • Is this use of PreparedStatements in a Thread in JAVA correct?

    - by Gormcito
    I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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  • In Java, can a final field be initialized from a constructor helper?

    - by csj
    I have a final non-static member: private final HashMap<String,String> myMap; I would like to initialize it using a method called by the constructor. Since myMap is final, my "helper" method is unable to initialize it directly. Of course I have options: I could implement the myMap initialization code directly in the constructor. MyConstructor (String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... // other initialization stuff unrelated to myMap } I could have my helper method build the HashMap, return it to the constructor, and have the constructor then assign the object to myMap. MyConstructor (String someThingNecessary) { myMap = InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } private HashMap<String,String> InitializeMyMap(String someThingNecessary) { HashMap<String,String> initializedMap = new HashMap<String,String>(); initializedMap.put("blah","blahblah"); // etc... return initializedMap; } Method #2 is fine, however, I'm wondering if there's some way I could allow the helper method to directly manipulate myMap. Perhaps a modifier that indicates it can only be called by the constructor? MyConstructor (String someThingNecessary) { InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } // helper doesn't work since it can't modify a final member private void InitializeMyMap(String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... }

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  • Selenium : Handling Loading screens obscuring the web elements. (Java)

    - by Sheldon Cooper
    I'm writing an automated test case for a web page. Here's my scenario. I have to click and type on various web elements in an html form. But, sometimes while typing on a text field, an ajax loading image appears , fogging all elements i want to interact with. So, I'm using web-driver wait before clicking on the actual elements like below, WebdriverWait innerwait=new WebDriverWait(driver,30); innerwait.until(ExpectedConditions.elementToBeClickable(By.xpath(fieldID))); driver.findelement(By.xpath(fieldID)).click(); But the wait function returns the element even if it is fogged by another image and is not clickable. But the click() throws an exception as Element is not clickable at point (586.5, 278). Other element would receive the click: <div>Loading image</div> Do I have to check every time if the loading image appeared before interacting with any elements?.(I can't predict when the loading image will appear and fog all elements.) Is there any efficient way to handle this? Currently I'm using the following function to wait till the loading image disappears, public void wait_for_ajax_loading() throws Exception { try{ Thread.sleep(2000); if(selenium.isElementPresent("id=loadingPanel")) while(selenium.isElementPresent("id=loadingPanel")&&selenium.isVisible("id=loadingPanel"))//wait till the loading screen disappears { Thread.sleep(2000); System.out.println("Loading...."); }} catch(Exception e){ Logger.logPrint("Exception in wait_for_ajax_loading() "+e); Logger.failedReport(report, e); driver.quit(); System.exit(0); } } But I don't know exactly when to call the above function, calling it at a wrong time will fail. Is there any efficient way to check if an element is actually clickable? or the loading image is present? Thanks..

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  • Is there a way to launch an aggressive and complete garbage collection in Java?

    - by Gnoupi
    For memory optimization reasons, I'm launching myself the garbage collector during profiling, to check if objects are correctly cleaned after disposing of them. The call to garbage collector is not enough, though, and it seems that there is no guarantee of what it will clean. Is there a way to call it, to be sure it will recover as much as it can, in profiling conditions (this would have no point in production, of course)? Or is "calling it several times" the only way to be "almost sure"? Or did I simply misunderstand something about the Garbage Collector?

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  • How to implement event listener in background of the main program in java?

    - by Johny
    Hi im a beginner so sorry for my question if it sounds naive. I want to implement a thread that runs in the background and listens all the time. By listening i mean, say it keeps check on a value returned from main thread and if the vaue exceeds certain figure, it executes some method, or say exits the program. If you could give me some idea or at least refer me to something useful, that'll be great.

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  • How to check if String value is Boolean type in Java?

    - by Ragnar
    I did a little search on this but couldn't find anything useful. The point being that if String value is either "true" or "false" the return value should be true. In every other value it should be false. I tried these: String value = "false"; System.out.println("test1: " + Boolean.parseBoolean(value)); System.out.println("test2: " + Boolean.valueOf(value)); System.out.println("test3: " + Boolean.getBoolean(value)); All functions returned false :(

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  • How can two programs talk to each other in Java?

    - by Arnon
    I want to ?reduce? the CPU usage/ROM usage/RAM usage - generally?, all system resources that my app uses - who doesn't? :) For this reason I want to split the preferences window from the rest of the application, and let the preferences window to run as ?independent? program. The preferences program ?should? write to a Property file(not a problem at all) and to send a "update signal" to the main program - which means it should call the update method (that i wrote) that found in the Main class. How can I call the update method in the Main program from the preferences program? To put it another way, is a way to build preferences window that take system resources just when the window appears? Is this approach - of separating programs and let them talk to each other (somehow) - the right approach for speeding up my programs?

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  • How does transmission created it's cross plataform app? It has from Qt/Mac to CLI interfaces!

    - by Somebody still uses you MS-DOS
    I'm amazed at Transmission, a BT client. It has a Mac, a GTK+, a QT, a Web Client and a CLI interface to it. I tried reading some of it's source to understand how he creates all these interfaces, but no luck. Does the developer creates them using a single ide? Or does he create the interface logic in each specific environment (specially mac), "exports" this window code and integrates with the main logic? How did the developers create this software with so many interfaces?

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  • Java JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • ASP.NET Custom Control With A Property That Is An Interface

    - by user129674
    I want to have a property on my custom control that is an interface type. For example: [ ToolboxData("<{0}:MyTextBox runat=server></{0}:MyTextBox"), ParseChildren(true, "Validation") ] class MyTextBox : WebControl { [ Category("Behavior"), Description("The validation to use"), DesignerSerializationVisibility(DesignerSerializationVisibility.Content), PersistenceMode(PersistenceMode.InnerDefaultProperty) ] public IValidation Validation { get; set; } } Then when I go to use my control in a web form I would like to be able to do: <my:MyTextBox ID="txt" runat="server"> <my:FancyValidator /> </my:MyTextBox> That way I will be able to define one class that could use any number of validators. When I try and do this now, I end up with an error saying: Type 'IValidator' does not have a public property named 'FancyValidator' What do I need to do to make this work? Thanks!

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  • Understanding reflection

    - by sdmiller
    I recently started work at a new company and a .net web application we have is built using reflection. I have only been out of school for a year and haven't worked with this concept. After studying the code... it looks like there is a single backend interface of type object that has about 20 classes that inherit from it. lots of generic gets and sets On the surface it looks like standard inheritance to me. I guess my question is, what makes this reflection? Is it because the interface is not strongly typed? Thanks

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  • java: how to make srollable panel with radio button and labels inside?

    - by Lucia
    Hi, I got a JScrollPane in which I want to place a list of radio buttons and labels. My problem is the panel doesn't scroll, I suppose it's because i didn't set a viewport, but how can I set it when I have to many components? My code looks something like this: JScrollPane panel = new JScrollPane(); JRadioButton myRadio; JLabel myLabel; for(int i = 0; i<100; i++){ myRadio = new JRadioButton(); myLabel = new JLabel("text"); panel.add(myRadio); panel.add(myLabel); } Thanks.

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  • Multithreaded java cache for objects that are heavy to create ?

    - by krosenvold
    I need a cache some objects with fairly heavy creation times, and I need exactly-once creation semantics. It should be possible to create objects for different CacheKeys concurrently. I think I need something that (under the hood) does something like this: ConcurrentHashMap<CacheKey, Future<HeavyObject>> Are there any existing open-source implementations of this that I can re-use ?

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  • Cross platform, Interactive text-based interface with command completion

    - by trojanfoe
    Does anyone know of a C++ library that will provide a text-based interactive interface? I want to create two versions of an application; a console based program that will perform whatever actions are given on the command line or interactively at the console as well as a GUI based program (Mac Cocoa and Windows MFC). Both versions will share a common C++ backend. For the console based program I would like similar history abilities to readline (which I cannot use as this application will be closed source) with command completion (Tab-activated for example). Perhaps there is something like this already available?

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